absolutely terrible wireguard performance on a 4ghz box - need tuning help

[Kyle Sanderson]

hi wireguard,

APU2C4 - AMD Embedded G series GX-412TC, 1 GHz quad Jaguar core with
64 bit and AES-NI support

There has to be a way to improve this. I'm getting 20-40MB/s (causing
a system load of 6 on this poor box) where SSHFS in comparison is
still able to fly. Traffic not traversing the tunnel is also,
strangely, impacted as well. I have the Intel i210AT controller, which
doesn't appear to have any offloading to it when wireguard is present.

ksoftirqd/0 spins at around 50%, ksoftirqd/1 spins around 20%, and the
other 12(!) wg-crypt threads hover around 20% respectively.
If I disable wg I'm able to get line-rate through acceleration.
The other 2 ksoftirqds sit around 5% respectively. kworker events
jumping between 10-25%.

Regrettably openwrt doesn't appear to have perf available...

K.